This invention relates to compositions, kits, methods, and apparatus for inhibiting muscular headaches and cerebral neurovascular disorders including, but not limited to, neurovascular headaches, migraines, cluster headaches, tinnitus, cerebrovascular spasm, ischemic disorders, seizures, central neuraxial motor, sensory, and cognitive deficits, degenerative, traumatic, or infectious lesions of the central nervous system, and cephalic inflammation including, but not limited to, meningeal inflammation, intracranial inflammation, extracranial inflammation. The invention also relates to apparatus and methods for directing intranasal administration of a composition to a selected portion of the nasal cavity, such as the superior portion or the dorsonasal portion.
Headache is a common symptom of numerous diseases and disorders including, but not limited to, migraine, muscle tension, systemic or intracranial infection, intracranial tumor, head injuries, severe hypertension, cerebral hypoxia, certain diseases of the eyes, nose, throat, teeth, and ears, and head pain for which no cause can be determined.
Infrequent headaches can often be determined to result from causes attributable to a particular experience of a patient, such as fatigue, fever, alcohol ingestion, muscle contraction, tension, or the like. The cause of persistent or recurrent headaches is often difficult to determine. Persistent or recurrent headaches include, but are not limited to, muscular headaches, such as tension or muscle contraction headaches, and neurovascular headaches, such as migraines and cluster headaches.
Cerebral neurovascular disorders (CNvDs) are characterized by one or more disturbances in the normal functioning of at least one component of the cerebral vascular or nervous system in a human. CNvDs include, for example, migraine, cluster headaches, other headaches of neurovascular etiology, tinnitus, and cerebrovascular spasm. Human patients afflicted with a CNvD experience a single episode of the disorder, recurrent episodes, persistent episodes, or some combination of these patterns. An individual episode is designated an acute CNvD.
Many CNvDs, such as cerebral vascular accidents, reversible ischemic neurological defects, and transient ischemic attacks (TIA), are associated with functional cerebral ischemia. These are often nonhemorrhagic and of thrombotic, embolic, and vasospastic etiologies. Furthermore, intracranial vasospasm commonly afflicts patients who have experienced an acute cerebral ischemic event such as a stroke and is often problematic following thrombolytic therapy. Numerous symptoms occur during and after acute cerebral ischemic events. Indeed, neurovascular headaches have a vasomotor component to them, which may be responsible for certain or many of the symptoms experienced by patients who are afflicted with prolonged or recurrent neurovascular headaches such as migraines and cluster headaches.
It has been theorized that headaches of neurovascular etiology, such as migraines, for example, result from release of neurotransmitters by trigeminal nerves, which innervate cerebral blood vessels (Moskowitz et al., 1979, Lancet 2:883-885). When disturbed, the trigeminal ganglion is capable of antidromic release of excitatory and other neurotransmitters that initiate sterile inflammation (Demarin et al., 1994, Funct. Neurol. 9:235-245; Moskowitz, 1984, Ann. Neurol. 16:157-168; Moskowitz, 1993, Neurol. 43(Suppl. 3):S16-S20). Studies of trigeminal stimulation, cerebral blood flow, and neuropeptides in animal models and in humans provide support for this theory (Goadsby et al., 1993, Ann. Neurol. 33:48-56; Goadsby et al., 1991, Headache, 31:365-370; Goadsby et al., 1990, Ann. Neurol. 28:183-187; Edvinsson et al., 1994, Cephalalgia 14:88-96). It has been postulated that changes in cerebral blood flow that are triggered by trigeminal stimulation are mediated by the sphenopalatine ganglion (hereinafter, the “SPG”) Goadsby et al., 1987, Am J. Physiol. 22:R270-R274; Lambert et al. 1984, J. Neurosurg. 61:307-315; Walters et al., 986, Stroke 17:488-494; Suzuki et al., 1989 Neuroscience 30:595-604).
Another theory posits that nitric oxide is a causative molecule of headaches of neurovascular etiology (Olesen et al., 1995, Cephalalgia 15:94-100). Because the SPG and related postsynaptic and neurovascular structures contain many cells which express nitric oxide synthetase, the SPG mediates the changes in cerebral blood flow that are triggered by trigeminal stimulation, according to this model.
Regardless of whether a neurotransmitter, nitric oxide, both, or neither are the causative agent of headaches of neurovascular etiology, it is clear that the SPG and other dorsonasal nerve structures are key complex structures for targeting the treatment of headaches of neurovascular origin, such treatment including, but not being limited to the treatment of the pain associated with such headaches. Methods of treating headaches of neurovascular etiology which have been described in the prior art have not provided sustained and effective relief from acute neurovascular headache episodes.
Other researchers have observed meningeal inflammation in the vicinity of head pain associated with migraine (Pappagallo et al., April 1999 presentation, Meeting of the American Academy of Neurology, Toronto, Canada). Certain aspects of head pain associated with migraine (e.g., throbbing headache, nausea, and sensitivity to light and sound) are similar to head pain associated with meningitis. Single photon emission computerized tomography confirmed enhanced permeability of meningeal blood vessels in patients experiencing migraine, which is a common finding among meningitis patients. It is believed by the inventor that meningeal inflammation may be associated with stimulation of, or transmission by way of, the trigeminal nerve and related neuronal structures.
Migraine
Migraine is a disorder characterized by persistent headache, which may be severe, which may be associated with visual and gastrointestinal disturbances, and which may also be recurrent. In certain cases, visual changes (designated “aura” by some practitioners) or other symptoms precede the onset of a migraine. Such prodromal symptoms may be due to intracranial vasoconstriction. The precise etiology of migraine is unknown. Reported evidence suggests that a genetically transmitted functional disturbance of intra- and extracranial circulation may be involved. Regional alterations in cerebral blood flow attributable to intracranial arterial vasodilation are known to accompany headache associated with migraine. Some investigators have attributed head pain associated with a migraine to substances released as a result of or associated with dilation of scalp arteries during an acute migraine episode (e.g., Berkow et al., ed., 1992, The Merck Manual of Diagnosis and Therapy, Merck Research Laboratories, Rahway, N.J., pp. 1425-1426).
Prodromal symptoms of an acute migraine episode include, but are not limited to, depression, irritability, restlessness, anorexia, scintillating scotomas, visual changes such as perception of stars or zig-zag lines, paresthesias, and hemiparesis. These prodromal symptoms may disappear shortly before the migraine is manifested, or may persist until or after the onset of the migraine.
The head pain associated with migraine may be unilateral or generalized. Nausea, vomiting, and photophobia often accompany migraines. Symptoms generally follow a pattern in an individual patient, except that unilateral head pain may not always be on the same side. Patients afflicted with migraine may experience migraines with a frequency between daily and only once in several months. An untreated acute migraine episode may endure for a long period, such as hours or days. Approximately 17% of adult women and approximately 6% of adult men experience migraines each year (Stewart et al., 1994, Neurol. (Suppl. 4):S17-S23; Lipton et al., 1993 Neurology 43(Suppl. 3):S6-S10; Osterhaus et al., 1992, PharmacoEconomics 2:67-76). Migraines may occur at any age, but usually begin between ages 10 and 30. Migraines often partially or completely remit after age 50. Frequently, a history of migraines may be ascertained in the genealogy of a patient afflicted with migraine.
Various nonspecific medical and surgical procedures have been recommended to decrease the frequency of recurrence of migraines. Such procedures include surgery, counseling, participation of the patient in biofeedback procedures, and administration of methysergide, propanolol, a calcium channel blocker such as verapamil, an ergotamine preparation such as dihydroergotamine, or a serotonin receptor agonist such as sumatriptan. Some procedures to decrease the frequency of recurrence of migraines may offer benefit to certain patients, but are not useful for alleviating the pain associated with an acute migraine episode once it has begun.
Treatments which have been recommended for the treatment of an acute migraine episode include administration of aspirin, codeine, a serotonin agonist such as sumatriptan, ergot, ergotamine, caffeine, a narcotic, butorphanol tartrate, meperidine, or a combination of these compounds. Administration of any combination of these compounds has not offered satisfactory or sustained relief from the pain or other symptoms associated with an acute migraine episode in many patients. Furthermore, numerous side effects have been reported to accompany administration of these compounds, including dizziness, nausea, somnolence, fatigue, chest pain, cardiac infarction, hypertension, hypertensive crisis, chest-, face-, and neck-hyperemia, gastrointestinal upset, sedation, drug dependence, and the like. In addition, certain of these compounds are contraindicated for numerous patients such as pregnant women, nursing women, patients using monoamine oxidase inhibitors, patients having a history of ischemic heart disease, ulcer, gastritis, kidney disease, liver disease, and other diseases.
Currently popular migraine treatments involve administration of a pharmaceutically active agent which interacts with a serotonin receptor on cerebral arterial surfaces (Goadsby, 1995, In: Migraine: Pharmacology and Genetics, Sandler et al., Eds., pp. 67-81; Cambridge et al., 1995, Brit. J. Pharmacol. 114:961-968; Ferrari et al., 1995, Euro. J. Neurol. 2:5-21). Serotonin receptor agonists include sumatriptan (IMITREX™, Glaxo Wellcome Inc., Research Triangle NC), zolmitriptan (ZOMIG™, Zeneca Pharmaceuticals, Wilmington, Del.), and rizatriptan (MAXALT™, Merck & Co., West Point, Pa.). Serotonin receptor agonists are believed to produce relief from an acute migraine episode by causing resumption of regulated cranial blood flow, thereby halting the acute migraine episode (Hamel et al., 1993 Mol. Pharmacol. 44:242-246). However, administration of serotonin receptor agonists is inefficient via intravenous, oral, and intrarectal gavage routes. These routes of administration result in systemic agonist distribution, which increases the availability of the agonist to hepatic tissue and to other sites where the agonists are metabolized. Furthermore, systemic distribution of one of an agonist results in distribution of the agonist to sites where the agonist produces undesirable side effects (Saper, 1997, Headache 37(Suppl. 1):S1-S14). Therefore, it would be advantageous to administer an agent which does not require systemic delivery.
Intranasal administration of lidocaine for the relief of pain associated with migraines has been investigated in a non-controlled study by Kudrow et al. (1995, Headache, 35:79-82). In that study, many patients experienced no relief and were on migraine prophylactic medication. In a controlled study, Maizels and co-workers evaluated the effectiveness of intranasally-administered lidocaine, a shorter-acting local anesthetic, for treatment of acute migraine episodes (Maizels et al., 1996, J. Amer. Med. Assoc. 276:319-321). High concentrations of lidocaine administered intranasally decreased head pain within fifteen minutes in 55% of the patients so treated. However, significant pain and associated symptoms persisted in many of these patients following treatment. A significant number of patients required further treatment with other types of migraine medication to attain acceptable relief. Furthermore, the acute migraine episode frequently rebounded or relapsed early after treatment, usually within the first hour.
Cluster Headaches
A cluster headache comprises a headache which is characterized by recurrent episodes of unilateral excruciating pain, usually occurring on the same side of the head of a patient. These headaches are typically oculofrontal or oculotemporal, with occasional radiation to the upper jaw, and are described as being of a boring, non-throbbing nature. Associated with the head pain are one or more autonomic accompaniments, including conjunctival injection, nasal congestion, lacrimation, rhinorrhea, body temperature elevation, vasodilation on the same side as that on which the pain is experienced, and edema beneath the eye. A cluster headache is usually of short duration, persisting for between fifteen and ninety minutes, and tends to occur in clusters—typically a few times a day for a period of six to twelve weeks. Months or years may pass between the clusters of headaches. Because headaches which appear to be identical to spontaneous cluster headaches may be induced by subcutaneous injection of histamine diphosphate, cluster headaches are also known as histamine headaches. Headaches having sensory similarity to cluster headaches may also be induced by administration of nitroglycerin to a human patient, for example by sublingual administration of 0.4 milligrams of nitroglycerin.
Methods which have been investigated for treating cluster headaches include administration of methysergide, a vasoconstrictor, a corticosteroid, oxygen, indomethacin, and intranasal administration of cocaine, which is a toxic shorter-acting local anesthetic with pronounced central effects and a vasoconstrictor, or lidocaine, which is also a shorter-acting local anesthetic (Barre, 1982, Headache, 22:69-73; Kittrelle et al., 1985, Arch. Neurol. 42:496-498). These investigations highlight that shorter-acting local anesthetics were effective to abort pain associated with a single individual headache episode that is only one of several headache episodes comprising a cluster headache, sometimes referred to as a cluster period. Large amounts of drug and repeated dosings were required to achieve these results. However, no investigation was made by those investigators of the ability of these shorter-acting local anesthetics to provide relief from all, or even more than one, of the typically short-duration headaches associated with a single cluster headache period. Clinically, intranasal administration of lidocaine has proven to be disappointing and is not widely used, nor is it included in recognized cluster headache treatment protocols.
Tinnitus
More than 37 million Americans are afflicted with tinnitus. Tinnitus is a condition characterized by a ringing, buzzing, roaring, or clicking sound perceived by a patient, a person observing the patient, or both, which seems to originate from the ear of the patient. Objective tinnitus is characterized by noise originating from the ear of a patient which can be perceived by a person examining the patient, while noise associated with subjective tinnitus can be perceived only by the patient. There are currently no truly effective treatment options available for tinnitus, which has been associated with instances of suicide in patients afflicted therewith. Treatment methods which have been attempted include surgical decompression of the eighth nerve, use of specialized hearing aids which mask the tinnitus, and infusion of drugs directly into areas of the brain involved in auditory sensory processing. None of these treatment methods has proven routinely effective.
Intra- and Extracranial Vasospasm
Intra- and extracranial vasospasm, hereinafter referred to as “cerebrovascular spasm,” results from contraction of smooth muscle tissue of a cerebral blood vessel. Cerebrovascular spasm interferes with cerebral blood supply and is associated with numerous symptoms, including muscle paralysis, visual changes, speech changes, and numerous ischemic symptoms of stroke. Vascular muscle tone is modulated by neural, humoral and local factors.
Disorders Manifested During or after and Associated with an Acute Ischemic Event
Causes of acute ischemic events include occlusive (i.e., thrombotic or embolic) processes, as well as vasospastic and other physiological processes and disorders, following the onset of which the affected tissue is insufficiently supplied with oxygenated blood. Manifestations during or after such events include, for example, tissue damage or death, vasospasm, vasodilation, vasomotor instability, muscle weakness, dysphasia, dysphonia, cognitive impairment, autonomic imbalance, and the like. These disorders may be alleviated by increasing oxygenated blood supply to the ischemic tissue. Increased blood supply to ischemic cerebral tissue may be effected, for example, by inducing dilation of an occluded cerebral blood vessel. Further by way of example, such increased blood supply may be effected by dilation of cerebral blood vessels proximal to an occluded vessel by increasing the flow of oxygenated blood or by increasing the pressure gradient across the occlusion, thereby decreasing the amount of watershed ischemia, decreasing the amount of damaged cerebral tissue, and increasing the amount of cerebral tissue which may be salvaged. Furthermore, facilitating venous drainage, by venodilation, decreases venous back pressure and increases forward flow of oxygenated blood.
Prior art methods of treating such disorders exhibit serious limitations. Thrombolytic therapy, for instance, is known to be effective to decrease the severity of cerebral damage caused by certain occlusive strokes if the therapy is performed soon enough after the onset of the occlusion. However, cerebrovascular spasm frequently follows, and decreases the success of the procedure and adversely affects patient outcome. A method of reducing the severity of an acute cerebral ischemic event by increasing early blood flow to the ischemic area and decreasing vasospasm is needed.
Anatomy of the Nasal Cavity
The structures associated with the nasal cavity are described, for example, in Williams et al. (eds., 1980, Gray's Anatomy, 36th ed., W.B. Saunders Co., Philadelphia, 1062-1065), especially at figures 3.78, 3.79, 3.80, 7.239, and 7.240 and the accompanying text. FIG. 1 herein is a diagram depicting the approximate location of the SPG in relation to the nasal cavity of a human.
The SPG is, in some texts, designated the “pterygopalatine ganglion.” The position, origin, branches, and distribution of the SPG may be understood by examining figures 7.177, 7.178, 7.179, and 7.181 and the accompanying text in Williams et al. (supra).
As the cited figures and text describe, the SPG is located below a region of epithelium in the posterior portion of the nasal cavity, inferior to and including the spheno-ethmoidal recess, and is therefore not readily accessible via the nostril.
Ropivacaine is a recently introduced amino amide local anesthetic that is commercially available as the S(levo)-enantiomer (Lee et al., 1989, Anesth. Analg. 69:736-738). Ropivacaine allows differential nerve block and exhibits intermediate distribution and clearance and a better systemic toxicity profile compared with other similar relatively long acting potent local anesthetics. In addition, ropivacaine also exhibits inherent vasoactive properties (deJong, 1995, Reg. Anesth. 20:474-481; Santos et al., 1990, Anesth. Analg. 70:262-266). Ropivacaine-HCl is commercially available as 0.25%, 0.5%, 0.75% and 1.0% (w/v) solution (NAROPIN™, Astra USA, Inc., Westborough, Mass.), and has been described, for example in international patent application publication number WO 85/00599.
Local anesthetics are known to block the generation and the conduction of nerve impulses, presumably by increasing the threshold for electrical excitation in the nerve, by slowing the propagation of nerve impulses, and by reducing the rate of rise of the action potential of the nerve. In general, the progression of anesthesia is related to the diameter, degree of myelination, and conduction frequency and velocity of affected nerve fibers. Generally, the order of loss of nerve function is as follows: (1) sympathetic and parasympathetic function, temperature and pain, and (2) touch, and, where applicable, (3) proprioception, and (4) skeletal muscle tone.
The rate of systemic absorption in a patient of a local anesthetic is dependent upon the total dose, the concentration, and the identity of the local anesthetic administered to the patient, the route of administration, the vascularity of the site of administration, and the presence or absence of vasoconstrictors such as epinephrine in the anesthetic composition. A dilute concentration of epinephrine (e.g., 1:200,000 or 5 micrograms per milliliter) usually reduces the rate of absorption and peak plasma concentration of the local anesthetic, sometimes prolonging the duration of the anesthetic effect.
The duration of the anesthetic effect at a given site of administration of a local anesthetic is dependent upon the total dose, the concentration, and the identity of the local anesthetic administered to the patient, the rate of systemic absorption, and often the presence or absence of a vasoconstricting or other agent in the anesthetic composition.
Systemic administration of a local anesthetic is not a practical method for delivery of the local anesthetic to provide lasting relief of headache pain in a human patient, due to known adverse reactions, occasionally including acute emergencies, associated therewith.
There remains a significant unmet need for effective methods of treating acute CNvDs such as persistent and recurrent headaches of neurovascular etiology, including migraines and cluster headaches. Particularly needed are compositions and methods which are effective for inhibiting an acute neurovascular headache episode.
Muscular Headaches
Muscular headaches are very common in the adult population. It is estimated that between about 3% and about 5% of patients who experience a muscular headache are afflicted with chronic muscular headaches, by which is meant that the muscular headache occurs more than fifteen days per month for a period of at least about six months. Analgesic addiction is a recognized problem in the treatment of patients afflicted with chronic muscular headaches.
Muscular headaches may be acute, as is the case for typical episodic tension headaches, which are related to contraction of muscles of the head and neck. Sustained contractions of skeletal muscles of the head, neck, face, and shoulders are associated with concurrent local chemical changes within skeletal muscle, and may give rise to pain. The pain may be localized or it may be referred, which means that the pain is perceived at a body location different than the location of muscle contraction. Muscle contraction headaches may also be chronic and associated with depression or with one or more other psychological problems. Muscle contraction headaches may also be associated with anatomic factors such as cervical arthritis, temporomandibular joint disorders, irritating lesions, pressure and mechanical stress, eye strain, or emotional stress or disorders.
Muscular headaches, including muscle contraction headaches and tension headaches, are recognized as the most common category of recurring head pain. In distinction from migraines, they are usually bilateral, often with occipital nuchal, temporal, or frontal predominance or with diffuse extension over the top of the cranium. The pain may be located in the back of the head and neck as well. Unlike migraine pain, the pain associated with a muscular headache is usually described as squeezing and vise-like in nature. Nausea, photophobia, and phonophobia are not generally associated with muscular headache episodes. The onset of a muscular headache episode is more gradual than the onset of a migraine or cluster headache episode, and muscular headache episodes are not generally associated with auras or prodromal symptoms. The onset of muscular headache episodes does not appear to be associated with physical activity by the patient. Once established, a muscular headache episode may persist, perhaps with minimal fluctuations in intensity, for weeks or months. Muscular headache is recognized as being present all day, day after day.
Although patients afflicted with migraine may be awaked from sleep, patients afflicted with a chronic muscular headache generally sleep undisturbed and perceive development or intensification of the headache soon after waking. About a third of patients afflicted with a muscular headache exhibit symptoms of depression. Migraine headaches may be complicated by tension headaches which persist and arouse fears of mass lesions, thereby leading to the performance of unnecessary diagnostic workups in many patients.
Muscular headaches are recognized as being a distinct class of headaches, distinguishable from headaches such as migraines or cluster headaches.
Muscular headaches are, in part, related to sustained contraction of the skeletal muscles of the scalp, face, neck, and shoulders. Sustained muscle contraction is related to local pathology, central influences, and multisystem modulation, and involves gamma efferent neuronal muscle spindle activation. Related monosynaptic conduction through the ventral horn augments both efferent neuronal discharge and muscle contraction. A cycle of pain, muscle spasm, local chemical changes, neural excitability, skeletal muscle blood vessel compression or spasm, and anxiety ensues. All types of persistent headaches lead to sustained cranial muscle contraction, but pain resulting from this type of sustained contraction is typified by an aching sensation, rather than by the characteristic squeezing pain associated with muscular headaches. Sometimes, surface electromyograph recordings of the craniocervical muscles show no evidence of persistent contraction. It is therefore widely suspected that muscular headaches are not caused solely by sustained cranial muscle contraction.
Generally, the pain associated with a muscular headache episode is mild to moderate in severity, although the pain becomes severe in many patients. Relaxation, massage, and common analgesic medications such as aspirin and acetaminophen are often effective to alleviate mild muscular headache pain. Codeine or other narcotic preparations, tranquilizers, and antidepressants are sometimes administered to patients experiencing more severe muscular headache pain. Unfortunately, many of these patients develop physical dependence on these agents and must be followed closely because of a significant incidence of addiction.
Nonetheless, the musculature of the head, neck, jaw, or upper back is tense and tender in many or most patients afflicted with a muscular headache, and one or more trigger points, or muscle knots, are often present. Cervical spine arthritis and temporomandibular joint disorders may contribute to the development of a muscular headache.
Treatments which have been recommended for the treatment of muscular headaches include reassurance and psychological support, massage of the head and neck, application of hot and cold packs, transcutaneous electrical neural stimulation, physical support (e.g., use of orthopedic pillows and the like), administration of aspirin compounds, acetaminophen compounds, non-steroidal anti-inflammatory drugs, tricyclic antidepressants, narcotic analgesics, oral muscle relaxants, with or without tranquilizers, muscle relaxants, and other analgesic compounds. These treatments are generally effective for alleviating mild- to moderate-intensity acute muscular headaches.
Some patients afflicted with either severe or chronic muscular headaches sometimes experience relief from their acute symptoms using these known treatments. However, many do not. Furthermore, over time, many patients who initially respond to one or more of these therapies become less responsive to these therapies, possibly because they develop a tolerance to known medications, or because the disease process progresses or increases. Additionally, symptoms may be influenced by psychological factors which may remain constant or worsen. The side effects which accompany administration of known medications are significant and may become more severe over time.
There remains a significant unmet need for effective compositions and methods of treating muscular headaches, including inhibiting muscle contraction headaches and tension headaches. The present invention provides compositions and methods which satisfy this need.
Systemic Delivery of a Pharmaceutically Active Agent
Numerous pharmaceutically active agents are useful when delivered systemically to a human patient. Systemic delivery of such agents can sometimes be effected by oral administration of a composition comprising the agent. However, many pharmaceutically active agents are degraded by, or otherwise react with acids, proteins, or other agents located in, the human gastrointestinal tract or the human liver or circulatory system, with the result that the agent loses its pharmaceutical usefulness. For this reason, many pharmaceutically active agents may not practically be administered by an oral route to achieve systemic delivery of the agent. In addition, gastrointestinal absorption of an orally administered medication may be impaired in a distressed patient, such as a patient experiencing a migraine or any severe headache.
Pharmaceutically active agents intended for systemic delivery to a human may be administered via an intravenous route using well known methods. However, such methods cause discomfort to the patient and often can be performed only in conjunction with frequent or continuous supervision by a medical professional.
Methods of topically administering compositions to a human tissue to achieve systemic delivery of a pharmaceutically active agent which is a component of the composition are known, including the use of transdermal or transmucosal pastes, cremes, liquids, solids and semisolids impregnated with the composition, and the like. Systemic delivery of a pharmaceutically active agent effected by topical administration methods are limited by the ability of the agent to diffuse through the tissue to which the composition is applied to reach blood vessels where the agent is absorbed and taken up for systemic delivery.
A significant, unmet need remains for compositions and methods which can be used to systemically deliver or to enhance systemic delivery of a pharmaceutically active agent to a human and which overcome the limitations of known systemic delivery compositions and methods.
The present invention provides compositions and methods which satisfy the needs described herein.